The phrases -/ . * and +/ . * are the determinant
and permanent of square matrix arguments. More generally,
the phrase u . v is defined in terms of a recursive expansion
by minors along the first column, as discussed below.

For vectors and matrices, the phrase x +/ . * y
is equivalent to the dot, inner, or matrix
product of math; other rank-0 verbs such as <. and *.
are treated analogously. In general, u . v is defined
by u@(v"(1+lv,_)) ,restated in English below.

The definition u@(v"(1+lv,_)) given above for the dyadic
case may be re-stated in words as follows: u is applied to
the result of v on lists of “left argument cells”
and the right argument in toto. The number of items in a
list of left argument cells must agree with the number in the right argument.
Thus, if v has ranks 2 3 and the shapes
of x and y are 2 3 4 5 6
and 4 7 8 9 10 11,then there are 2 3 lists
of left argument cells (each shaped 4 5 6);and if
the shape of a result cell is sr,the overall shape
is 2 3,sr .